just read through most of this thread over the last few days.
I recently purchased a 07 330d m sport(bought privately), fitted with the 18" MV3 wheels, thinking the wheel cracking issues were confined to the 19" MV4 wheels.
3 weeks in and i now find i have 2 cracked rear wheels!
Car is still fitted with, Bridgestone run flats.
When i discovered the first wheel cracked i called the local main BMW dealer, who suprise suprise are not interested, car not bought from them and no longer under warranty.
So i bought a refurbed wheel to replace the cracked wheel.
While having this changed over i had the tyre place, remove the opposite wheel to check it over, and yes it also has a very small crack in it. Its not loosing air at the moment but it can only get worse.
Not sure its worth pursuing with BMW, thought please???